Coriolis Ocean database for ReAnalysis CORA3.4 Product User Manual Version 1.0 R&D Coriolis Team February 11, 2013 IFREMER - Pointe du Diable -29280 Plouzané - web: www.coriolis.eu.org/Science/Data-and-Products Contents 1 Dataset overview1 1.1 History of the dataset....................................1 1.1.1 Previous versions of CORA.............................1 1.1.2 Main changes for the CORA3.4 version......................2 1.2 Data sources.........................................2 1.3 Organisation of the dataset..................................2 1.3.1 Files formats - structure...............................2 1.3.2 Type of files and data type..............................3 1.3.3 The Index files....................................4 2 Data quality 5 2.1 Quality flags.........................................5 2.2 Adjusted parameter versus parameter............................6 2.3 Data processing.......................................6 2.3.1 Climatological test..................................6 2.3.2 Check of duplicates profiles.............................8 2.3.3 XBT bias correction.................................8 2.3.4 Feebacks from model assimilation.........................9 2.3.5 Non monotonic pressures..............................9 2.3.6 Duplicate pressure-depth..............................9 2.3.7 Global consistancy checked with Objective analysis tool..............9 3 Data coverage 13 A Tables 19 i CHAPTER 1 Dataset overview CORA3.4 dataset is a product of MyOcean2 FP7 project. It stands for the historical global dataset of MyOcean2V3. This document is a Product User Manual, it aims to describe the content of the dataset and how to use it properly. Some of the validation steps refer to the article [Cabanes et al.(2013)Cabanes, Grouazel, von Schuckmann, Hamon, Turpin, Coatanoan, Paris, Guinehut, Boone, Ferry, de Boyer Montégut, Carval, Reverdin, Pouliquen, and Le Traon] . 1.1 History of the dataset The program Coriolis has been setup at Ifremer at the beginning of the 2000’s in the wake of the devel- opment of operational oceanography in France. The project was launched in order to provide ocean in situ measurements to the French operational ocean analysis and forecasting system (Mercator-Océan) and to contribute to a continuous, automatic, and permanent observation networks. The Coriolis data centre has been set up to gather, qualify [Coatanoan and Petit de la Villéon(2005)] and distribute data from the global ocean both in real and delayed time. The Coriolis database is a real time database as it is updated every day as new data arrive. On the contrary, the CORA dataset corresponds to an extraction of all in situ temperature and salinity profiles from the Coriolis database at a given time. All the data is then re-qualified. CORA is meant to fit the needs of both re-analysis and research projects. However, dealing with the quantity of data required by re-analysis projects and the quality of data required by research projects remains a difficult task. Several important changes have been made since the last release CORA02, both in the production procedure (to be able to release yearly reanalysis) and quality checks applied to the data. These changes are fully described in this document. 1.1.1 Previous versions of CORA Two previous versions of CORA have already been released by the Coriolis data center and the R&D Coriolis team: 1. CORA01 in 2007. It contains data from 2002 to 2006 2. CORA02 in 2008. data from 1990 to 2007. To produce such a dataset the Coriolis data center proceed basically in three steps: 1 CORA3.4 Documentation, Rev. 1.0 1. Data passes through a statistical quality check based on objective analysis method (see [Gaillard et al.(2009)Gaillard, Autret, Thierry, Galaup, Coatanoan, and Loubrieu] for further de- tails).This statistical check produced alerts on doubtful profiles. 2. All doubtful profiles are visually checked, and profiles are flagged - if necessary - in the Coriolis database. 3. Data is extracted from the Coriolis database (to produce netCDF files). 1.1.2 Main changes for the CORA3.4 version • A new procedure is now used to produce the dataset: This sequence of processing steps is fully described in the paper Cabanes et al. 2013: • A set of quality checks is performed on the data (see Cabanes et al. 2013 for more details) • A check of duplicates was re-run on the whole dataset. • An XBT bias correction has been applied. • CORA3.4 release covers the period 1990-2011 (such as CORA3.3) but ICES (CIEM) CTD data have been added to the dataset. 1.2 Data sources Data submitted to, or obtained by, the Coriolis Data Centre which contains profiles of temperature and/or salinity were potential data source for CORA3.4 dataset. The CORA3.4 dataset thus corresponds to the Coriolis database at the date of the CORA3.4 retrieval (22th of January, 2013). For CORA3.3 (previous version), the data retrieval has been spread over time (see table 1.1). Data Span Date of retrieval 1990-2008 25-May-2010 2009 09-September-2010 2010 22-03-2011 2011 01-09 04-10-2011 2011 10-12 22-03-2012 Table 1.1: Dates of retrieval for CORA3.3 The Coriolis centre receives data from Argo GDAC, French research ships, GTS flow, GTSPP, GOSUD GDAC, MEDS, voluntary observing and merchants ships, moorings (TAO-TRITON-PIRATA-RAMA plus coastal moorings), and the World Ocean Database (not in real time for the last one and for CTD only). CORA thus contains data from different types of instruments: mainly Argo floats, XBT, CTD, XCTD, and moorings. 1.3 Organisation of the dataset 1.3.1 Files formats - structure Files structure is the same as for the distribution of the Argo profiles data and it is fully described in the argo-dm-user manual, section 2.2. Each netcdf files contains many profiles (number given by 2 Chapter 1. Dataset overview CORA3.4 Documentation, Rev. 1.0 the dimension N_PROF) and a profile contains measurements of different variables (e.g. temperature, salinity) performed at different pressures or immersion (the number of vertical levels is given in the netCDF file by the N_LEVELS dimension) taken as the instrument is being dropped or risen vertically in the water column. For surface-only data, the profile consists of a single measurement. For moored buoys and drifting buoys, a profile is a discrete set of concurrent measurements from the instruments placed at different depths. All the variables in a file are defined for Argo float profiles, but most of these variables still have the same signification for other types of profile (e.g. XBT or CTD profiles). Guidance for the users Each profile has a unique identifier in the Coriolis database and the CORA dataset which is the DC_REFERENCE number. Please, refer to this DC_REFERENCE number if you want to make a feedback on a specific profile to the Coriolis data centre. The variable PLATFORM_NUMBER is the platform identifier that is assigned for the life of the platform (e.g. Profiling floats, moored buoys, ...). For measurements collected from research vessels or merchant ships-of-opportunity the PLAT- FORM_NUMBER is the vessel/ship identifier. 1.3.2 Type of files and data type In CORA3.4, data is sorted in 9 types depending mainly on the data sources and resolution. Most of these types are those defined for the GTSPP (PF, CT, XB, BA and TE) while others are ‘in-house’ types (OC, MO and HF). All the data are stored in netcdf files using the same format as the one defined for the Argo program and a naming convention that indicates the data type. Files are stored in yearly directories. There is one file per day and per type. The file name is of the form: CO_DMQCGL01_YYYYMMDD_PR_TT.nc This file contains all the raw data of the date YYYYMMDD and of the data type TT. • PF files : data from Argo floats directly received from DACS (real Time and delayed mode if available). These data have a nominal accuracy of 0.01° and 0.01 PSU and are transmitted with full resolution. • XB files : XBT or XCTD data received from research and opportunity vessels have accuracy within 0.03° to 0.1° for temperature and 0.03 to 0.1 PSU for salinity. • CT files : contains CTD data from research vessels (accuracy on the order of 0.002° for tempera- ture and 0.003 PSU for salinity after calibration) but also data from sea mammals equipped with CTD (accuracy is on the order of 0.01° for temperature and 0.02 PSU for salinity but can be lower depending of the availability of reference data for post-processing, see Boehme et al, 2009) and received from MNHN and some sea Gliders. • OC files : Others CTD and XCTD data coming from the high resolution CTD dataset of the World ocean database 2009. • MO files : Mooring data are mostly from TAO TRITON RAMA and PIRATA mooring and have accuracy generally comparable to Argo floats (except for S near surface). • TE and BA files : The two last categories are for all the data transmitted trough the GTS (data from Argo floats not yet received at the DACS, mooring, XBT,...). This transmission system imposes limitation on the accuracy: data is truncated two and one places beyond decimal point for TE and BA type respectively. • HF files: High Frequency data coming from coastal moored buoys (max 3 levels of immersion, max depth<200m, with less than 0.01° of variation in position and more than one measure per 1.3. Organisation of the dataset 3 CORA3.4 Documentation, Rev. 1.0 day on at least 10 days in a year). The confidence on the quality of such data is much lower than offshore classical moorings because of the lack of climatology in such area. • IC files: ICES CTD from CIEM database distributed over the whole time span.